Given: Annual salary average: $22,040 Annual Social security benefit: 42% of salary average Monthly bill: $1,375 $22,040 x 42% = $9,256.80 per annum $9,256.80 / 12 mos = $771.40 per month $1,375 – 771.40 = $603.60 Since, Christina only receives $771.40 per month from her Social Security benefit, she has to take $603.60 from her savings each month to help pay her monthly bill of $1,375.